As disclosed in copending applications Ser. No. 300,046 (Walter I), filed Sept. 8, 1981 now U.S. Pat. No. 4,405,792; Ser. No. 495,977 (Walter II), filed May 19, 1983; Ser. No. 497,026 (Ramachandran I) and Ser. No. 497,027 (Ramachandran II), both filed May 23, 1983; and Ser. No. 511,831 (Ramachandran and Ranken), Ser. No. 511,832 (Ramachandran, Ranken, and Wiegand), and Ser. No. 511,913 (Ranken and Ramachandran), all filed July 8, 1983, it is known that 4-(halophenyl)pyridines are useful as intermediates in the preparation of bactericides, such as the 1-alkyl-1,4-dihydro-4-oxo-7-pyridinyl-3-quinolinecarboxylic acids of Sterling Drug's U.S. Pat. Nos. 3,753,993 (Lesher et al.), 3,907,808 (Lesher and Carabateas), and 4,118,557 (Lesher).
Walter I and II, Ramachandran I and II, Ramachandran and Ranken; Ramachandran, Ranken, and Wiegand; and Ranken and Ramachandran all prepare their 4-(halophenyl)pyridines by the aromatization of the corresponding halocyclohexenylpyridines. It would be desirable to be able to prepare them by a technique that would not require an aromatization step.
March, Advanced Organic Chemistry, McGraw-Hill (New York), pp. 482-484 (1977), shows that some aromatic compounds can be brominated in the presence of a Lewis acid, and Gordon et al., "The Swamping Catalyst Effect. VI. The Halogenation of Isoquinoline and Quinoline," Journal of Organic Chemistry, vol. 29, pp. 329-332 (1964) teaches the effect of the use of an excess of a particular Lewis acid--aluminum chloride--in directing the halogenation of isoquinoline and quinoline.